wc -l < medals.txt
grep -E '中国|中国香港|中国台北' medals.txt | sort -k5,5nr
sort -t, -k4,4nr medals.txt | head -5 | cut -d, -f1
sort -t, -k2,2nr medals.txt | head -5 | cut -d, -f2 | paste -sd+ | bc
